Knives are one of the oldest tools made by humans. Since the time that the first knives were made from stone, a lot has changed. Knife smiths have developed the art of blade forging. Blade designs, the forging process and steel materials have been improved over time in an effort to hold knife blade edges as sharp as possible. Even so, a knife must still be sharpened from time to time.
As will be understood by someone with ordinary skill in the art, knife blades are designed to have sharp edges. Knife blade edges are formed by the intersection of two surfaces, or “bevels”.
There are many different variations of blade profiles, including among others: flat, wedge, convex, concave and chisel. Edge profiles can be convex, flat, concave, or chisel.
Many knife blade edge profiles are formed by the intersection of two angled (flat, convex, or concave) bevels—these types of blades are generally referred to herein as double sided, or alternatively, as double bevel. As compared to a double bevel edge, a chisel edge profile (sometimes referred to herein as a chisel ground blade, or as a “single-sided” blade) is formed by the intersection of an angled bevel and a flat side—the flat side being parallel to (having a zero degree angle relative to) the blade centerline.
As will be understood by someone with ordinary skill in the art, knife blade edges are sharpened by grinding (polishing, or wearing down, as with an abrasive) the surfaces that form the edge. That is, a double sided, or double bevel, edge, is generally sharpened by grinding the respective angled bevels with a sharpening element; a conventional single sided, or chisel ground, edge, is generally sharpened by grinding the single angled bevel.
It is difficult to consistently sharpen a knife blade correctly, because the person sharpening the blade must match the angle of the blade's edge, with the surface of the sharpening device.
Folding knives are carried and used by many people. Folding knives are especially valuable to people on the go who, from time to time find the need for a knife but who need to conserve space and provide for safety in carrying a sharp implement. For example, campers and hunters may pack fixed blade knives for use at camp, but also may carry a folding knife in their pocket for use while hiking, hunting, or the like. Mountain climbers and other sports enthusiasts may carry a folding knife in a backpack or pocket for use, just in case they need it. Military personnel may carry folding knives while on a mission.
A person that carries a folding knife should be able to rely on the sharpness of the knife. However, a person who carries a folding knife may forget to unpack the knife and sharpen it. Moreover, appropriate equipment is needed to correctly sharpen a blade. Because appropriate sharpening equipment is often cumbersome or may require electricity to operate, it is unlikely that a person would carry such equipment in the field. Many portable field sharpeners currently exist, however, it is difficult to use these sharpeners and difficult to maintain the correct angle. Additionally, sharpening equipment is a separate piece of equipment; it is often not convenient to carry such separate equipment. Further, serrated knife blades can be extremely difficult to sharpen. A better way of sharpening folding knives is needed.